US1984846A - Ignition composition - Google Patents

Description

Patented Dec. 18, 1934 UNITED STATES A PATENT OFFICE IGNITION COMPOSITION No Drawing. Application October 13, 1933, Serial No. 693,476

3 Claims.

This invention relates to an improved ignition composition and more particularly to such a composition adapted for use as the topcharge in an electric blasting cap.

Ignition compositions of the type covered by this invention have various applications. For example, they may be used advantageously as the top charge in composit'on blasting caps, both of the ordinary fuse type, where the ignition charge is fired by the spit of the fuse, and in electric blasting caps, in which the initiation of the ignftion charge is brought about by means of the heat developed by the passage of an electric current through a bridge wire of very small diameter. A second use is as the ignition charge in electric squibs, which are adapted to bring about the explosion of a defiagrating explosive such as black powder, and which require an ignition charge developing a considerable flame. An additional use is as a priming composition in percussion caps. A further use is in igniters generally, particularly those of the match-head type. In this case, the ignition material may be cemented to the firing bridge wire by forming the ignition composition into a paste by the use of various solvents and other materials.

Blasting caps 01 both the fuse and electric type, as commonly used, are of the class called composition caps, in that they contain more than one explosive charge, for example a base or secondary charge at the closed end of the metal shell container and a primary charge superimposed on the base charge. As secondary detonatin'g compounds, tetranitromethylaniline (tetryl), trinitrotoluene, pentaerythritol tetranitrate, picric acid, diazodinitrophenol and the like have been most commonly used, while the primary charges have customarily comprised mercury fulminate, either alone or mixed with an oxidizing agent such as potassium chlorate, and lead azide.

When lead azide alone is employed as a primary charge, difliculty is frequently met in the ignition of this material, so that it is necessary to use an additional ignition charge. As such a charge, mixtures of lead sulfocyanate with oxidizing agents and fuels have been used, as well as lead hypophosphite compositions, nitrocellulose by itself, and many other compositions, both in loose and compressed form. An object of my invention is an improved ignition composition possessing desirable properties for such use. A further object is amomposition especially adapted for initiation by electrical means. A still further object is an ignition comheight of 5".

position suitable for such use and possessing low firing current requirements. Additional objects will be disclosed as the invention is further described.

I have found that the foregoing objects are obtained by the employment of tetramethylene diperoxide dicarbamide as an ignition compound or ingredient of an ignition composition. This compound has the empirical formula CsHiaosNi, and may be used either by itself or incorporated with other materials, for example oxidizing agents and fuels.

While tetramethylene diperoxide dicarbamide may be ignited by various methods, I prefer to use electrical ignition means, since this compound has properties favorable to this method of firing, a current of 0.280 to 0.330 amperes being suflicient to bring it to satisfactory ignition. The compound has the advantage also of a satisfactory degree of sensitiveness to impact, such that it is not unduly sensitive and dangerous to handle. As a matter of fact, its sensitiveness is such that no detonations take place when a steel ball, weighing 8.3 grams, is dropped on the compound on a steel surface from a On the other hand, detonations result almost invariably when the same steel ball is dropped from the height of 12", other conditions being the same.

As has been stated previously, tetramethylene diperoxide dicarbamide may be used by itself or in mixtures with oxidizing agents. Suitable compositions of this nature are 75 to 95% tetramethylene diperoxide dicarbamide with 25 to 5% potassium chlorate. Other oxidizing agents such as sodium nitrate, potassium nitrate,

barium nitrate, potassium perchlorate and the like may be used also. If desired, an additional fuel may be incorporated with the above ingredients; for example, smokeless powder or nitrocellulose in other form.

Tetramethylene diperoxide dicarbamide may be prepared by the method described by Girseweld and Siegen (Berichte der Deutschen u. Chemischen Gesellschaft 1914, V. 47, p. 2464), according to which urea is dissolved in a mixture of hydrogen peroxide and formaldehyde, to which solution nitric acid is added. The whole is then cooled and diluted with water. The white crystalline tetramethylene diperoxide dicarbamide is precipitated out under these conditions. In the method described above, the ingredients urea, hydrogen peroxide, and formaldehyde are used in the molecular proportions of 0.5:1:1. other proportions of these materials may be used, however, and other mineral acids than nitric acid. I have found it preferable, also, to prepare the compound by first preparing a solution of urea in formaldehyde, then adding to the solution a cold mixture of hydrogen peroxide and nitric acid. If desired, acid materials such as sodium acid sulphate may be employed instead of a mineral acid. The method of. preparation of the compound, however, is not a part of my invention. Tetramethylene diperoxide dicarbamide may be graphically represented by the following structural formula:

Tetramethylene diperoxide dicarbamide is adapted according to my invention for use in various types of initiators where a charge is desired capable of emitting a satisfactory ignition flame. It may be employed, for example, as a priming charge in percussion caps, either by itself or mixed with oxidizing agents, fuels, sensitizers and the like. Similarly, it may be used for electric ignition in match-head type igniters or in electric squibs. My preferred method of use, however, is as a top charge in blasting caps, preferably in electric blasting caps of the composition type. When used in such a manner, I may employ a base charge of tetryl or other suitable secondary detonating compound, on which a superimposed primary charge, preferably of lead azide, is used. Above this is placed the ignition composition, either tetramethylene diperoxide dicarbamide by itself or in suitable mixtures with the other ingredients previously mentioned. In such an electric blasting cap, a satisfactory loading of the various charges comprises 5 grains of base charge, 3 grains of primary charge and 2.5 grains of ignition composition. It should be understood, however, that the tetramethylene diperoxide dicarbamide composition may itself act as the primary charge, since my invention consists in the use of tetramethylene diperoxide dicarbamide as an ignition material regardless of the other materials mixed with it or adjacent to it.

While tetramethylene diperoxide dicarbamide may be employed as ignition composition in ordinary blasting caps, where such composition is ignited by the spit of a fuse, the compound is in some cases not sufiiciently sensitive to flame. The

material may be rendered sufliciently sensitive by limited only as indicated by the following patent claims:

I claim:

1. An ignition charge for an initiator, said charge comprising tetramethylene diperoxide dicarbamide.

2. An ignition material as the top charge in a composition blasting cap, said ignition materialcomprising tetramethylene diperoxide dicarbamide.

3. An ignition material as the top charge in a composition electric blasting cap, containing a suitable base charge and a primary charge of lead azide, said ignition material comprising tetramethylene diperoxide dicarbamide.

CHARLES P. SPAETH.